Since Parker and her actor-husband Matthew Broderick announced that they were expecting twins via a surrogate, Parker said the Florida woman, identified by Star magazine as Michelle Ross, has been hounded by tabloids and paparazzi.

"The most unsavory things have been done," she told "Access Hollywood." "She's had her phone hacked, her personal computer information hacked, she's had threats against her and true harassment. ... She's had friends threatened and family threatened and she's had family of friends threatened.

"It keeps me up every night," added Parker, who lives in New York City. "It's really incredibly upsetting to think of her so far away and me not being able to do something, beyond what I'm legally allowed to do."

Few would question Parker's concern or her desire to protect her surrogate. But when concern crosses the line to control, surrogate moms and the "intended mothers" they are carrying for will not only clash, but an experience that is often considered joyous can easily turn into nightmare.

That's what happened to Stephanie from California -– who did not want her full-name or location used to protect her privacy -- the first time she acted as a surrogate for a Northern California woman five years ago.

Only 24 at the time, Stephanie blames her inexperience for getting into a situation that still haunts her to this day. "I literally almost lost my marriage and my own sanity," she told ABCNews.com.

The first time Stephanie, who worked through an agency, met her intended mother, or IM, at a restaurant, the 40-year-old scientist burst into tears and hugged Stephanie. She told Stephanie about how she endured a stillborn birth and multiple miscarriages, and the younger woman agreed to be her surrogate.

"I didn't ask a lot of questions," she said, looking back. "I knew that I could possibly help her, that this was her last option, and I just jumped right into it."

Michelle (not her real name) from Missouri, believes most surrogate experiences are positive, but it's the bad ones you read about. An uncompensated surrogate for her husband's cousin, she said some surrogates set themselves up for a bad experience. "They don't do their homework, they rush into things too quickly and it's not the right personality fit," she said. "A lot of them are younger, so maturity could be an issue."

Surrogacy Turns to Nightmare

Stephanie's problems began with the transfer of four of the woman's embryos to Stephanie's uterus. Three of them took, and Stephanie says the IM flipped out, saying she couldn't handle triplets and the doctor would need to use selective reduction. It was the first time Stephanie, a devout Christian, had ever even heard about such a procedure and she was against it. Fortunately, by the next ultrasound, only two embryos remained.

Still, the idea of Stephanie carrying twins worried the IM, who lived two hours north. She called Stephanie and asked if she could move into her home during the pregnancy. "She told me she wanted to experience this as much as if she was carrying the twins herself," Stephanie recalled.

With her husband working nights and two young children of her own under the age of 3, Stephanie and her husband agreed.